1. Field of the Invention
The present invention relates to a lubricant composition for a limited slip differential (LSD) of a car. More specifically, it relates to a lubricant composition for LSD which is excellent in oxidation stability and the prevention ability of the chattering (abnormal noise) of an LSD device incorporated in the differential of a car and which can be suitably applied to LSD of a studless tires-carrying car whose demand increases mainly in cold districts.
2. Description of the Prior Art
In general, as an LSD device incorporated in the differential of a car, a wet multiplate clutch is used, and its differential controlling force is maintained by the frictional force of a metallic plate. A lubricant for this LSD is required to have extreme-pressure properties of a GL-5 class, and thus the lubricants containing a sulfur-phosphorus additive and a friction modifier have been heretofore used.
However, these lubricants are poor in frictional properties, so that abnormal noise which is called chattering is generated during the operation of differential gears, or a metallic friction plate is abraded in a short period of time. In consequence, it is often difficult to maintain the initial performance of the differential gears for a long period of time.
Accordingly, it has been desired to develop a lubricating oil which is excellent in frictional properties and durability thereof and which minimizes the abrasion of a metallic friction plate.